1. Field of the Invention
The present invention relates to test technology for an integrated circuit, and more particularly to a method and apparatus for sampling a power supply current for performing frequency analysis of the power supply current flowing in the integrated circuit when a test signal is applied thereto, and to a storage medium onto which is stored a control program for controlling the sampling apparatus.
2. Related Art
A method such as noted above of sampling the power supply current of an integrated circuit was used in the past in order to perform frequency spectrum analysis of the power supply current of the integrated circuit.
For example, as noted in a paper titled “Fast Fault Detection by Analyzing the Power Spectrum of Supply Current” by Kazuhiro Sakaguchi and Shigehiro Kamimura SEMI Technology Symposium 98, 3-77 to 3-83, there is a method for sampling the power supply current for the purpose of determining the frequency spectrum of the power supply current.
In the method described in the above-noted reference, sampling of the power supply current is performed while applying a test pattern to an integrated circuit.
In the method described in the above-noted reference, however, there is a problem that there exists a possibility that the power supply current information for the power supply current flowing in the integrated circuit under test (DUT; device under test) is not completely obtained.
The reason for this is that the circuits forming the power supply or current measurement unit and the device under test have capacitive components and inductive components, so that even if the application of the test pattern is ended, power supply current continues to flow for an amount of time established by the time constant of the circuit.
For this reason, in order to obtain complete information with regard to the power supply current related to the operation of a device under test to which a test pattern is applied, it is necessary, simultaneously with the completion of application of the test pattern, to not stop the sampling of the power supply current, but rather to continue the sampling for some time thereafter.
Accordingly, it is an object of the present invention, in consideration of the above-described drawback in the prior art, to provide a method and apparatus for sampling a power supply current of an integrated circuit, which obtains all complete information with regard to a power supply current flowing in an integrated circuit when a test pattern is applied to the integrated circuit, and to provide a storage medium onto which is stored an associated control program for executing this sampling method.